1. Field of the Invention
The present invention relates to a wound electrochemical device and a method of manufacturing the same.
2. Related Background Art
Conventionally known wound electrochemical devices include those of a type using an elliptical or flat “″planar wound body” formed by flatly winding a long electrode (see Japanese Patent Application Laid-Open Nos. 2007-194130, 2006-286431, 2000-67907, and 2001-345115). In this type, the flat portion realizes a multilayer structure of electrodes, while bent portions formed upon winding can keep a mechanical strength of the electrodes and suppress deformations thereof. They have a flat form after winding and thus are advantageous in terms of space for use. However, it is necessary for electrodes to connect with leads having a specific thickness, which makes them hard to attain a significantly flat form.
For such a problem, in order to securely attain a flat form, it has been proposed to provide an inwardly convex structure at the center portion of the wound body, thereby absorbing bulges caused by the leads (see Japanese Patent Application Laid-Open No. 2003-109869).